Microbicidal composition

ABSTRACT

A synergistic microbicidal composition comprising a non-ionic surfactant and glutaraldehyde and a method for inhibiting the growth of microorganisms in an aqueous medium.

This invention relates to microbicidal compositions containing glutaraldehyde and a surfactant.

A composition containing 5-chloro-2-methylisothiazolin-3-one, 2-methylisothiazolin-3-one and a nonionic dispersant is disclosed in U.S. Pat. No. 4,295,932. The composition contains a 3:1 mixture of 5-chloro-2-methylisothiazolin-3-one and 2-methylisothiazolin-3-one, and a copolymer of ethylene oxide and propylene oxide. However, there is a need for combinations of microbicides having synergistic activity against various strains of microorganisms to provide effective control of the microorganisms. Moreover, there is a need for such combinations containing lower levels of individual microbicides for environmental and economic benefit. The problem addressed by this invention is to provide such synergistic combinations of microbicides.

The present invention is directed to a synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₆H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:1.

The present invention is further directed to a synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₉H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:4.

The present invention is further directed to methods for controlling the growth of microorganisms in aqueous media by adding to an aqueous medium a nonionic surfactant as described herein and glutaraldehyde in the ratios described herein.

As used herein, the following terms have the designated definitions, unless the context clearly indicates otherwise. The term “glutaraldehyde” refers to glutaraldehyde, (1,5-pentanedial) CAS No. 111-30-8. The term “microbicide” refers to a compound capable of inhibiting the growth of or controlling the growth of microorganisms; microbicides include bactericides, fungicides, viricides, archaeacides and algaecides. The term “microorganism” includes, for example, fungi (such as yeast and mold), bacteria, virus, archaea and algae. The following abbreviations are used throughout the specification: ppm=parts per million by weight (weight/weight), mL=milliliter. Unless otherwise specified, temperatures are in degrees centigrade (° C.), references to percentages are percentages by weight (wt %) and amounts and ratios are on an active ingredient basis, i.e., total weight of glutaraldehyde and the nonionic surfactant. Numbers of polymerized units of propylene oxide or ethylene oxide are number averages.

The synergistic microbicidal composition of the present invention comprises a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₆H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:1.

The invention further comprises: a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₉H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:4, alternatively 7.6:1 to 1:3.4.

The present invention is further directed to a method for inhibiting the growth of bacteria, preferably anaerobic sulfate-reducing bacteria, in an aqueous medium by adding: (a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₆H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:1

The present invention is further directed to a method for inhibiting the growth of bacteria, preferably anaerobic sulfate-reducing bacteria, in an aqueous medium by adding: a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₉H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:4, alternatively 7.6:1 to 1:3.4.

Preferably, each of the compositions is substantially free of microbicides other than the nonionic surfactant and glutaraldehyde, i.e., it has less than 1 wt % of microbicides other than the nonionic surfactant and glutaraldehyde based on total weight of active ingredients, preferably less than 0.5 wt %, preferably less than 0.2 wt %, preferably less than 0.1 wt %. Preferably, when the nonionic surfactant and glutaraldehyde are added to an aqueous medium, the medium is substantially free of other microbicides, i.e., it has less than 1 wt % of microbicides other than the nonionic surfactant and glutaraldehyde based on total weight of active ingredients, preferably less than 0.5 wt %, preferably less than 0.2 wt %, preferably less than 0.1 wt %.

The compositions of this invention may contain other ingredients, e.g., defoamers and emulsifiers. The microbicidal compositions of the present invention can be used to inhibit the growth of microorganisms or higher forms of aquatic life (such as protozoans, invertebrates, bryozoans, dinoflagellates, crustaceans, mollusks, etc) by introducing a microbicidally effective amount of the compositions into an aqueous medium subject to microbial attack. Suitable aqueous media are found in, for example: petroleum processing fluids; fuel; oil and gas field functional fluids, such as injection fluids, hydraulic fracturing fluids, produced fluids, drilling mud, completion and workover fluids; oil and gas pipelines, separation, refining, transportation, and storage system; industrial process water; electrocoat deposition systems; cooling towers; air washers; gas scrubbers; mineral slurries; wastewater treatment; ornamental fountains; reverse osmosis filtration; ultrafiltration; ballast water; evaporative condensers; heat exchangers; pulp and paper processing fluids and additives; starch; plastics; emulsions; dispersions; paints; latices; coatings, such as varnishes; construction products, such as mastics, caulks, and sealants; construction adhesives, such as ceramic adhesives, carpet backing adhesives, and laminating adhesives; industrial or consumer adhesives; photographic chemicals; printing fluids; household products, such as bathroom and kitchen cleaners; cosmetics; toiletries; shampoos; soaps; personal care products such as wipes, lotions, sunscreen, conditioners, creams, and other leave-on applications; detergents; industrial cleaners; floor polishes; laundry rinse water; metalworking fluids; conveyor lubricants; hydraulic fluids; leather and leather products; textiles; textile products; wood and wood products, such as plywood, chipboard, flakeboard, laminated beams, oriented strandboard, hardboard, and particleboard; agriculture adjuvant preservation; surfactant preservation; medical devices; diagnostic reagent preservation; food preservation, such as plastic or paper food wrap; food, beverage, and industrial process pasteurizers; toilet bowls; recreational water; pools; and spas.

The specific amount of the microbicidal compositions of this invention necessary to inhibit or control the growth of microorganisms in an application will vary. Typically, the amount of the composition of the present invention is sufficient to control the growth of microorganisms if it provides from 1 to 5000 ppm (parts per million) active ingredients of the composition. It is preferred that the active ingredients (i.e., nonionic surfactant and glutaraldehyde) of the composition be present in the medium to be treated in an amount of at least 10 ppm, preferably at least 100 ppm, preferably at least 200 ppm. It is preferred that the active ingredients of the composition be present in the locus in an amount of no more than 5000 ppm, preferably no more than 2000 ppm, preferably no more than 1000 ppm, preferably no more than 500 ppm, preferably no more than 300 ppm, preferably no more than 200 ppm. In a method of this invention, a composition is treated to control microbial growth by adding, together or separately, the nonionic surfactant and glutaraldehyde, in amounts that would produce the concentrations indicated above.

EXAMPLE

Surfactants and biocides were evaluated for synergy by determining the synergy index (S.I.) of the combination. Synergy index was calculated based on the concentration required to achieve a certain level of bacterial kill when the two antimicrobial compounds (A and B) alone and in combinations. The test organism was anaerobic sulfate-reducing bacteria Desulfovibrio longus ATCC #51456. Surf. A R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₆H Surf. B R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₉H where R¹ is 2-ethylhexyl.

Example: Synergistic Effect of Glutaraldehyde and Surf A and B Against Anaerobic Sulfate-Reducing Bacteria

Inside an anaerobic chamber (Bactron anaerobic chamber), a deoxygenated sterile salt solution (3.1183 g of NaCl, 1.3082 mg of NaHCO₃, 47.70 mg of KCl, 72.00 mg of CaCl₂, 54.49 mg of MgSO₄, 172.28 mg of Na2SO₄, 43.92 mg of Na₂CO₃ in 1 L water) was inoculated with Desulfovibrio longus ATCC 51456 to a final bacterial concentration of 10⁶ to 10⁷ CFU/mL. Aliquots of this cell suspension were then treated with glutaraldehyde, and each of Surf A and B at selected active concentrations. After incubation at 35° C. for 2 hours, viable bacteria in the aliquots were enumerated using serial dilution method. Synergistic combinations and their biocidal efficacy as well as Synergy Index were summarized in Table 1 and Table 2.

The test results for demonstration of synergy of the combinations are shown in the tables below. Each table shows the results for combinations of two components against the microorganisms tested with incubation times; the end-point activity in ppm measured by the level of kill for compound A alone (CA), for component B alone (CB), and the mixture (Ca) and (Cb); the calculated SI value; and the range of synergistic ratios for each combination tested. SI is calculated as follows: Ca/CA+Cb/CB=Synergy Index (“SI”)

Wherein:

-   -   Ca=Concentration of biocide A required to achieve a certain         level of bacterial kill when used in combination with B     -   CA=Concentration of biocide A required to achieve a certain         level of bacterial kill when used alone     -   Cb=Concentration of biocide B required to achieve a certain         level of bacterial kill when used in combination with A     -   CB=Concentration of biocide B required to achieve a certain         level of bacterial kill when used alone         When the sum of Ca/CA and Cb/CB is greater than one, antagonism         is indicated. When the sum is equal to one, additivity is         indicated, and when less than one, synergism is demonstrated.

TABLE 1 Biocidal efficacy of glutaraldehyde (Glut) and Surf. A against anaerobic sulfate-reducing_bacteria, and Synergy Index Concentration (active Active weight ppm) for complete ratio of bacterial kill in 2 hours Synergy Glut:Surf. A Glut Surf. A Index 1:0 13.2 0.0 8:1 8.8 1.1 0.68 6.7:1  5.9 0.9 0.45 5:1 5.9 1.2 0.46 3:1 3.9 1.3 0.31 1:1 3.9 3.9 0.34 0:1 0.0 >100

TABLE 2 Biocidal efficacy of glutaraldehyde (Glut) and Surf. B against anaerobic sulfate-reducing bacteria, and Synergy Index Concentration (active Active weight ppm) for 99.99% ratio of bacterial kill in 2 hours Synergy Glut:Surf. B Glut Surf B Index 1:0 5.9 0.0 7.6:1  3.9 0.5 0.67 3.4:1  3.9 1.2 0.67 1:1 3.9 3.9 0.70  1:3.4 3.9 13.2 0.79 0:1 0.0 >100 

The invention claimed is:
 1. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₆H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:1.
 2. A method for controlling the growth of microorganisms in an aqueous medium; the method comprising adding to the aqueous medium the synergistic microbiocidal composition of claim
 1. 3. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure: R¹O(CH₂CH(CH₃)O)₅(CH₂CH₂O)₉H where R¹ is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:4.
 4. A method for controlling the growth of microorganisms in an aqueous medium; the method comprising adding to the aqueous medium the synergistic microbiocidal composition of claim
 3. 